Pumps



Jan. 14, 1958 E. A NORDELL ETAL 2,819,678

PUMPS Filed April 28, 1951 324 3304 ffl-Q 5 IN V EN TOR. [owl/v A Nassau. :ll- [l DFN/Nb A. KATHE J/a al www? A. Tar/verm t .BY a L a l Arrakfxs United States Patent@ PUMPS Edwin A. Nordell, Cleveland, Edmund A. Kathe, Columbus, and Arthur A. Thyreen, Cleveland Heights, Ohio; said Nordell and said Thyreen assignors to The Metal Craft Co., Inc., Cleveland, Ohio, a corporation of Ohio Application April 28, 1951, Serial No. 223,468

29 Claims. (Cl. 10S-150) This invention relates to improvements in pumps and more particularly, to a novel means to reciprocate the pumping element, such as a piston or diaphragm pumping element.

Most pumps require a mechanism to convert the rotational motion of a driving motor into a reciprocating motion for the pumping element. Heretofore, this mechanism has always been expensive to manufacture. The mechanism has always used many intricate parts, which were difficult to manufacture and had to be machined to small tolerances.

The novel pump and mechanism of this invention is inexpensive to manufacture and its parts neither are intricate nor require complicated machining operations.

One of the objects of the present invention is to provide in a pump of the type described a simple means for converting the rotational drive of a motor into a reciprocating motion for the pumping element, such as a piston or diaphragm pumping element.

Another object of the present invention is to provide in a pump of the type described a simple means, as set forth above, including a spring to drive the pumping element during one stroke of the pumping cycle and to keep the remainder of said means constantly in driving engagement.

Another object of the present invention is to provide in a pump of the type described a simple means, as set forth above, to reciprocate a diaphragm in which the diaphragm is resilient, and a surface of the diaphragm is a part of said means. This resiliency keeps the remainder of said means in driving contact and moves said diaphragm during one stroke of the pumping cycle.

Other features of our invention reside in the arrangement and design of the parts for carrying out their appropriate functions.

. Other objects and advantages of our invention will be apparent from the accompanying drawings and description and the essential features will be set forth in the appended claims.

In the drawings, Fig. l is a longitudinal sectional view of a piston type pump of this invention;

Fig. 2 is a vertical sectional view taken along the line 2 2 of Fig. l;

Fig. 3 is a longitudinal sectional view of a modified form of a piston-type pump;

Fig. 4 is a longitudinal sectional view of a third pump modification, illustrating another diaphragm type pump;

Fig. 5 is a longitudinal sectional view of a fourth pump modication, illustrating another diaphragm type pump;

Fig. 6 is a longitudinal sectional view of a fifth pump modification, illustrating another diaphragm type pump, while Fig. 7 is a sectional view of another type check valve which could be readily used with any of the above pumps.

Figs. l and 2 illustrate one form of pump of this invention. The pump, shown generally at 10, consists of a pump housing 11 having a tubular main body lz'closed "ice by a cap 13. This cap may be attached to the main body by screws or any other common type fastening means. The pump housing has a threaded inlet 14 and a threaded outlet 15, as conventionally found on most fluid pumps. A spring loaded inlet ball check valve 16 and an outlet check valve 16a is within the pump housing in tluid `c0mmunication with the inlet and outlet, respectively. These valves constitute means preventing the flow out of the pumping chamber 21, to be further described hereinafter, through the inlet and means preventing ow into said pumping chamber through said outlet. In other words, the valves constitute means normally preventing reverse ow through the inlet and outlet.

The pumping means for this pump consists of a piston 17 having a larger diameter 1S and a rearwardly extending shank 19 of reduced diameter. An axial, longitudinal bore retains the check valve 16 remote from the larger diameter section of the piston.

The means to reciprocate the pumping means or piston will next be described. it consists of a rotatably mounted driver member 22 adapted to be rotated about its axis by a motor or other power source. This member consists of a shaft 23 and a disc 24. A thrust bearing 25 'consisting of a carbon seal ring absorbs the axial thrust of the driver member. A driving surface 26 on the face of the disc is adapted to co-act with a reciprocably driven surface 27 carried by said pumping means or piston. The spherical ball or rollable element 28 drivingly connects, engages or contacts the two surfaces. Surface 27 is an inclined cam surface contacting the freely rotatable ball while surface 26 has a raceway or circular groove 30. This raceway lies in a plane perpendicular to the rotational axis of the driver member and serves as :a means to drivingly retain the ball. The raceway has a retaining shoulder 30a equal distance from the axis to engage the driving surface of the ball farthest from the axis. A resilient means is provided to keep the surfaces andball member in driving contact and to drive the piston through one-half of its cycle. This resilient means consists of a helical spring 31 mounted between the larger diameter 18 and a sleeve 32. This sleeve is fixed in the main p ump body 12 and slidably mounts the shank 19 of the piston.

The outlet check valve 16a has a cap 16a' engaging the end of the sleeve which projects beyond the end of the piston shank. A spring 16a resiliently retains the cap of check valve 16a against the sleeve while spring 16', mounted in a recess of the cap, retains the ball of check valve 16 against its seat. The pumping chamber 21 in this pump is between the rear of the shank 19 and cap 16a', or, in other words, between the inlet check valve 16 and the outlet check valve 16a.

Fig. 3 shows the second type of pump of this invention. The pump, generally indicated at 110, has a pump housing 111 consisting of a main body portion 112 and a cap 113 attached thereto by any suitable means. The fluid inlet 114 and fluid outlet 115 are in the pump housing. Ball check valves 116 and 1165: are in the .inlet and in iluid communication with the outlet, respectively, and serve the same purpose as valves 16 and 16a in Figs. l and 2.

The pumping means consists of a piston 117 having a head 118 and a shank 119, extending to the rear of said head. A pumping chamber 121 is formed between the piston head 11,8 and check valve 116. The check valve 11641 is located near the piston head in a longitudinal bore of the piston.

The means to reciprocate the pumping means or piston is somewhat similar to the structure in Figs. l and 2. A rotatably mounted driver member 122 is adapted to be driven by a motor. lt consists of a shaft 123 and a disc 124. A thrust bearing 125 absorbs the end thrust of gamers the driving surface 126' of the disc. A reciprocably driven surface 127 is carried by said piston or pumping means. The tapered roller or rollable element 128 drivingly connects, engages or contacts the surfaces, and said roller engages the inclined cam surface 127 of the driver surface and the raceway 131) of the driving surface 126. This raceway lies in a plane perpendicular to the rotational axis of the driver member and serves as a means to drivingly retain the tapered roller. The raceway has a retain* ing shoulder equal distance from the axis to engage the driving surface of the ball farthest from the axis. A resilient means is also provided to keep the surfaces and tapered roller member in driving contact to move the piston during its leftward stroke. The means consists of the helical spring 131 and the pressure fluid adapted to contact the rear of the piston to assist the spring. This pressure fluid is from the pressure side of the pump since the back of the piston is in uid communication with outlet r115. The spring surrounds the piston shank and is mounted between the rear of the piston head and the cap of the pump housing. The piston head may or may not have a piston ring 136, as desired.

Fig. 4 illustrates a third type of pump of this invention. The pump, shown generally at 210, consists of a pump housing 211 having a main body 212 and a cap 213. The pump inlet 214 and the pump outlet 215 in the cap contain spring loaded ball check valves 216 and 216a respectively. These valves are for the same purpose asdthze respective valves in the pump shown in Figs. 1 an A pumping means or diaphragm 220 is mounted within the pump housing. The diaphragm is attached at its edges between the cap and main body of the housing to form a chamber 221 for pumping the fluid.

Means is provided to reciprocate the diaphragm or pumping means. It consists of a rotatably mounted driver member 222 adapted to be driven by a motor. The driver member has a disc 224 mounted on a shaft 223, and a thrust bearing 225 to absorb any end thrust from the driver member. This thrust bearing is of the ball bearing type, as illustrated in Fig. 5. Of course, any of the common types of thrust bearings could be used herein. A driving surface 226 contains a raceway 230 loosely holding a spherical ball or rollable element 228. This raceway is similar to raceway 30 in Fig. l. A driven member 229 is connected to the center of the diaphragm and provides a reciprocably driven surface 227 carried by said pumping means or diaphragm. The spherical ball drivingly connects, engages or contacts the two surfaces 226, 227. The driven member has an inclined cam surface 227 contacting the ball, and the operation of these surfaces and ball to reciprocably drive the pumping means is similar to the operation of the pumps disclosed in Figs. l and 3. A resilient means 231 or helical spring keeps the surfaces and ball member in driving contact and. provides the leftward or expansion stroke of the diaphragm. The spring surrounds the shank of the driven member or piston 229 and is mounted between the rear face of the piston head and the shoulder 233 of the pump housing.

The fourth modification of this invention is shown in Fig. 5 by pump 31.0. It has a pump housing 311 consisting of a main body 312 and a cap 313. The cap has an inlet 314 and outlet 315 with spring ball loaded check valves 316 and 31611, respectively, therein. The valves serve the same purpose as valves 16 and 16a in Figs. 1 and 2.

The pumping means consists of a diaphragm 320 attached at its edges to the pump housing between the main body portion 312 and the cap 313. A pumping chamber 321 is formed between the diaphragm and the cap and in uid communication with the inlet and outlet.

A means to reciprocate the pumping means or diaphragm is also provided. This consists of a rotatably mounted Vdriver member 322 adapted to be rotated about its axis by a motor drive. This member has a shaft 323 4 and a disc 324 with a thrust bearing 325 absorbing the end thrust. The driving surface 326 of the disc is an inclined cam surface facing the diaphragm. The reciprocably driven surface 327 is carried by said pumping means or diaphragm 320. The spherical ball or rollable element 323 drivingly connects, engages or contacts these surfaces and rides in the raceway 33t). This raceway is formed on the driven surface 327 of the diaphragm bounded by the annular shaped projection 336e facing the cam. The raceway lies in a plane perpendicular to the rotational axis of driver member 322 and serves as a means to drivingly retain the ball. The shoulder or projection 330:1 is equal distance from the rotational axis so that it engages the driving surface of the ball farthest from the axis. The resilient means to keep the surfaces and ball member in driving contact and to move the diaphragm during its leftward stroke is provided by the resiliency of the diaphragm itself. This diaphragm 320, as well as diaphragm 229', may be made of any resilient material, such as a copper-beryllium alloy, plastic, leather or other composition.

The fifth modification of this invention is shown in Fig. 6 by pump 416. lt has a pump housing 411 consisting of a main body 412 and a cap 413. The cap has an inlet 414 and an outlet 415 kwith spring loaded ball check valve 16 and 416e, respectively, therein to serve the same purpose as the check valves in Fig. 1.

The pumping means consists of a diaphragm 420 attached at its edges to the pump housing between the main body portion 412 and the cap 413. A pumping chamber 421 is formed between the diaphragm and the cap in fluid communication with the inlet and outlet.

A means to reciprocate the diaphragm or pumping means is also provided in this pump. This consists of a rotatably mounted driver member 422 adapted to be rorated about its axis by a motor drive of any desired type. This member has a shaft 4-23 and a disc 424 with a thrust bearing 425 absorbing the end thrust. The driving surface 26 of the disc is in the form of an inclined cam facing the diaphragm. A driven member 429 is connected to the center of the diaphragm and provides a reciprocably driven surface 427 carried by said pumping means or diaphragm. A spherical ball or rollable element 428 drivingly connects, engages or contacts these surfaces and rides in the raceway 431i of surface 427. This raceway structure is similar to that found in the Fig. 1 pump modiication. The resilient means to keep the surfaces and ball member in driving contact and to move the diaphragm during its leftward stroke is provided by helical spring 431 engaging the diaphragm on its right-hand side. This diaphragm may be made of any of the common type of diaphragm materials, for example, those set forth in describing diaphragm 320. A pilot bar 434, mounted on driver member 429, is adapted to slide in the axial pilot bore 435 in driver member 422. The bottom of the pilot hole is vented by vent hole 43551 communicating with the atmosphere. Hence, the pilot bar will assure that all points on the diaphragm located equal distance from the axis will always reciprocate together and be in vertical alignment. The vent hole 435a prevents formation of a vacuum at the bottom of bore 435 during reciprocation of the pilot.

Although vent hole 435a is disclosed as extending the full axial length of shaft 42.3, it might extend radially outward to the atmosphere just outside of pump housing 411.

The pilot bar 434 and pilot bore 435 of the Fig. 6 modification could be used with diaphragm 321i of Fig. 5. Also, driven member 429 may be used in Fig. 5 on the diaphragm, if desired.

The operation of all the pumps, shown in Figs. 1 to 6 may well be described at one time. The driver member is rotatably driven either clockwise or counterclockwise. This member rotates and drives the rollable element, a

tapered roller or ball, so as to drive or reciprocate the pumping means, either the piston or diaphragm. The movement of the ball between the cam surface and ball raceway is a combination of a rolling and sliding contact. The driver member rolls the ball up the cam surface so as to reciprocate the driven member or ptunping means against the action of the resilient biasing means or spring. For example, rotation of disc 24 in Fig. l about the longitudinal axis of the pump in one direction will, if no ball slippage would occur and piston 17 would not rotate, rotate ball 28 about this same axis at about half the speed while this ball rolls on the facing surfaces of both disc 24 and piston 17 so that piston 17 will be reciprocated. Any tendency for piston 17 to rotate about this axis is restrained by the friction between the ends of spring 31, stationary sleeve 32 and piston 17; by the inertia of piston 17; and by the low friction of the small area of contact of the rolling contact of ball 28. The rollable element is held against the outer shoulder or projection of the racen way by the centrifugal force of the moving parts. The reciprocation of the pumping means expands and contracts the pumping chamber 21, 121, 221, 231, or 421 so as to suck the liquid in through the inlet and inlet check valve and then pump it out at a higher pressure through the outlet and outlet check valve of the pump.

This invention naturally contemplates that any type of a thrust bearing may be used be-tween the driver member and the pump housing. It may be a carbon seal ring, shown at 25 and 12S, or a ball type thrust bearing, as shown at 225 and 325, or even the common type of ordinary tlat bearing surfaces. The invention also contemplates that the pistons, in the Fig. l and Fig. 3 modifications, may or may not have a piston ring, as desired. The spring loaded ball check valve in Figs. 1 to 6 need not necessarily be of this design. For example, Fig. 7 shows a common type in which the ball 516 is forced upward against the tapered seat 516 by the pressure of the fluid instead of the spring. This prevents flow in the upward direction but downward ilow will unseat the ball and bring it downward against a non-circular opening 516" in the lower part of the check valve housing. ln high speed pump operation, it has been found that no ball check valve is needed but merely a restricted aperture will serve the purpose. Any of the above means may be used Ito prevent flow of the liquid out of the pumping chamber through said inlet and to prevent iow into the pumping chamber through said outlet.

Although the pistons 17 and 117 are freely rotatable as well as reciprocable in said pump housings, this invention contemplates that a key and keyway could be provided to limit their motion to a pure reciprocating motion. Although the raceway, driving surface, and driven surface are co-axially aligned in each of the pumps described, this co-axial relationship need not exist.

This invention also contemplates that the raceway for the rollable element and the cam may be on either the driver or driven surfaces. For example, in Fig. l, the raceway could be on piston 17 and the cam surface on disc 24 to resemble the Fig. 6 modification. The driving action would be exactly the same. The ball raceways need not be of annular shape, as shown at 3th, but may be a at surface with a projection, as shown at 331m, or merely a flat surface with the inner bore of the pump housing preventing the outward movement of the ball. Any type of a raceway adapted to drivingly retain the rollable element would be suitable.

We claim:

1. A pump, comprising a housing having a pumping chamber with a fluid inlet and a fluid outlet connected thereto; means preventing flow out of said chamber through said inlet; means preventing ow into said chamber through said outlet; a pumping means in the fiuid flow path between said inlet and said outlet; and a means to reciprocate said pumping means including a driver memi ber rotatable about an axis and having a driving surface,

a reciprocably driven surface carried by said pumping 6 means, 'a Vfreely rollable element drivingly contacting the surfaces; one of said surfaces being an inclined cam surface, and resilient means to keep said surfaces and rollable element in driving contact.

2. A pump, comprising a housing having a pumping chamber with a fluid inlet and fluid outlet connected thereto; means preventing ilow out of said chamber through said inlet; means preventing ow into said chamber through said outlet; a pumping means in the fluid flow path between said inlet and outlet, said pumping means being reciprocable along a straight line axis; and a means to reciprocate said pumping means consisting of a driver member rotatable about an axis and having a driving surface, both of said axes extending in the same direction, a reciprocably driven surface carried by said pumping means, a freely rollable element drivingly contacting the surfaces with the rotational axis of said element movable relative to both the driving and driven surfaces, one of said surfaces being an inclined cam surface, the other of said surfaces having a raceway lying in a plane perpendicular to at least the axis followed by one of said members to retain said rollable element, and resilient means to keep said surfaces and rollable element in driving contact.

3. A pump, comprising a housing having a pumping chamber with a fluid inlet and a fluid outlet connected thereto; means preventing flow out of said chamber through said inlet; means preventing flow into said chamber through said outlet; a pumping means in the fluid flow path between said inlet and said outlet; and a means to reciprocate said pumping means including a driver member, rotatable about an axis and having a driving surface, a reciprocably driven surface carried by said pumping means, a tapered roller drivingly contacting the surfaces, and one of said surfaces having an inclined cam surface.

4. A pump, comprising a housing having a pumping chamber with a fluid inlet and a iluid outlet connected thereto; means preventing flow out of said chamber through said inlet; means preventing flow into said chamber through said outlet; a pumping means in the fluid flow path between said inlet and said outlet; and a means to reciprocate said pumping means including a driver member rotatable about an axis and having a driving surface, a reciprocably driven surface carried by said pumping means, a ball rolling with respect to and drivingly contacting the surfaces, one of said surfaces being an inclined cam surface, and resilinet means to keep said surfaces and ball member in driving contact, whereby the frequency of reciprocation is adapted to be approximately one-half the R. P. M. of the driver.

5. A pump, comprising a housing having a pumping chamber with a uid inlet and a fluid outlet connected thereto; means preventing flow out of said chamber through said inlet; means preventing dow into said chamber through said outlet; a pumping means in the fluid flow path between said inlet and said outlet; and a means to reciprocate said pumping means including a driver member rotatable about an axis and having a driving surface, a reciprocably driven surface carried by said pumping means, a ball drivingly contacting -the surfaces, one of said surfaces being an inclined cam surface, the other of said surfaces extending generally perpendicular to said axis and means providing an annular raceway on only said driver member to retain said ball, said ball having true rolling contact with said driven surface.

6. A pump, comprising a housing having a pumping chamber with a fluid inlet and uid outlet connected thereto; means preventing flow out of said chamber through said inlet; means preventing ilow into said chamber through said outlet; a pumping means in the fluid llow path between said inlet and outlet; and a means to re-l ciprocate said pumping means including a driver member rotatable about an axis and having a driving surface, a reciprocably driven surface carried by said pumping means, each surface being rotatable about a common axis, a tapered roller drivingly contacting the surfaces, one of esigere said surfaces being an inclined cam surface, the other of said, surfaces having a raceway lying in aplane perpendicular to said axis to retain said tapered roller, and resilient means to keep said surfaces and tapered roller member in driving contact.

7. A pump, comprising a housing having a pumping chamber with a fluid inlet and uid outlet connected thereto; means preventing tiow out of said chamber through said inlet; means preventing llow into said chamber through said outlet; a pumping means in the fluid flow path be* tween said inlet and outlet; and a means to reciprocate said pumping means including a driver member rotatable about an axis and having a driving surface, a reciprocably driven surface carried by said pumping means, a spherical ball drivingly contacting the surfaces, one of said surfaces being an inclined cam surface, the other of said surfaces having a ball raceway lying in a plane perpendicular to said axis to retain said ball, and resilient means to keep said surfaces and ball member in driving contact.

8. A pump, comprising a housing, a disc rotatably mounted about an axis in said housing and adapted to be driven by a motor, said disc having a circular groove in its driving face forming a raceway, a piston reciprocably mounted in said housing, an angular cam front face on said piston, said disc, raceway and piston being co-axial, a rollable element in said raceway engaging said cam surface, a spring engaging said piston to keep said co-axial members and rollable element in driving contact, said housing having an inlet and an outlet in uid communication with a pumping chamber in said housing, means in said pump preventing flow out of said pumping chamber through said inlet, and means in said pump preventing ow into said pumping chamber through said outlet.

9. A pump, as set forth in claim 8, said rollable element being a tapered roller, said piston having a co-axial longitudinal bore in fluid communication with said outlet and said inlet, said last mentioned means being a check valve in said bore near said cam face, and the housing having a passageway whereby the pressure fluid from said outlet is adapted to contact the rear of said piston to assist said spring.

10. A pump, comprising a housing, a` disc rotatably mounted about an axis in said housing and adapted to be driven by a motor, .said disc having a circular groove in its driving face forming a raceway, a piston reciprocably mounted in said housing, an angular cam front face on said piston, said disc, raceway and piston being co-axial, a rollable element in said raceway engaging said cam surface, a spring engaging said piston to keep said coaxial members and rollable element in driving contact, said housing having an inlet and an outlet in uid communication with a pumping chamber in said housing, means in said pump preventing ow out of said pumping chamber through said inlet, and means in said pump preventing flow into said pumping chamber through said outlet, said rollable element being a spherical ball, said piston having a co-axial longitudinal bore adapted to have iluid communication with said outlet and said inlet through said pumping chamber, said means to prevent ow out of said inlet being a check valve in said bore remote from said cam face, said piston having a shank of reduced diameter, a sleeve mounted in said housing and slidably mounting said shank, said sleeve protruding beyond the back end of said shank, and said means to prevent how into said outlet being a spring loaded cap engaging the protruding end of said sleeve.

1l. A pump, comprising a housing; a diaphragm attached at its edges to said housing and forming a chamber within said housing; said housing having an inlet and an outlet in fluid communication with the chamber; means in said inlet and said outlet preventing reverse ow; means to reciprocate said diaphragm; said last mentioned means including a driver member being rotatable abou-t an axis and having a driving surface, a driven surface carried by said diaphragm, a ball drivingly contacting said surfaces,

one of said surfaces having a cam surface, the other of said surfaces having a shoulder equal distance from the axis of said driving member to engage the driving surface of said ball farthest from said axis, and resilient means to keep said surfaces and ball in contact.

12. A pump, comprising a housing; a diaphragm attached at its edges to said housing and forming a chamber within said housing; said housing having an inlet and an outlet in uid communication with the chamber; means in said inlet and said outlet preventing reverse flow; means to reciprocate said diaphragm; said last mentioned means including a driver member rotatable in said housing about an axis, a reciprocably driven member connected to said diaphragm, a spherical ball drivingly contacting the members, a cam surface on one of said members contacting said ball, means on the ball engaging surface of the other of said members to drivingly retain the ball, and a helical spring mounted between said housing and said driven member to keep said members and said ball in driving engagement.

13. A pump, as set forth in Claim 12, said driver member having an axial pilot bore facing said diaphragm, a pilot bar connected to said driven member and positioned to slidably engage said bore.

14. A pump, as set forth in claim 12, wherein said cam surface is on said driven member.

l5. A pump, comprising a housing; a resilient diaphragm attached at its edges to said housing and forming a chamber within said housing; said housing having an inlet and an outlet in lluid communication with the cham ber; means in said inlet and said outlet preventing reverse ow; means to reciprocate said diaphragm; said last mentioned means including a driver member in said housing rotatable about an axis, a cam surface on said driver member facing said diaphragm, said diaphragm having an annular shaped projection facing said cam, a ball drivingly engaging said cam surface and the surface of said diaphragm surrounded by said annular projection.

16. A pump, as set forth in claim l, wherein said pumping means is mounted by an annular periphery in said housing so that it is not positively restricted against rotation at said periphery in said housing by breaks in the continuity of said annular periphery.

17. A pump, as set forth in claim l, including means for mounting said reciprocably driven surface in said housing for free rotation about said axis.

18. A pump, as set forth in claim 4, wherein only said driving surface has a ball raceway retaining groove therein, and said driven surface is composed of straight radial zones extending inwardly and outwardly from and in contact with said ball.

19. A pump, as set forth in claim 18, wherein said groove is annular in form.

20. A pump, as set forth in claim 4, wherein said surfaces are designed so that the driving friction between said ball and driving surface is always greater during pump operation than between said ball and driven surface.

21. A pump, as set forth in claim l, wherein said driven surface serves as the iluid contacting and compressing surface of said pumping means.

22. A pump, as set forth in claim 1, wherein said pump has said fluid path between said inlet and outlet extending through the space between said surfaces with this space serving as walls of the pumping chamber.

23. A pump, as set forth in claim l, wherein one of said surfaces has a hole therethrough in fluid communication with the iiuid being pumped.

24. A pump, as set forth in claim l, wherein said driven surface and said pumping means have a bore therethrough adapted to provide fluid communication between the pumping chamber and said outlet.

25. A pump, as set forth in claim 24, wherein a check valve is located in said bore.

r26. A pump, as set forth in claim 1, wherein said resilient means restrains said driven surface against rotation by said rollable element.

27. A pump, comprising a housing having a pumping chamber with a Huid inlet and a fluid outlet connected thereto; a driver member mounted for rotation about an axis in said housing and having a driver surface thereon, a pumping piston having a reciprocably driven surface facing said driving surface to form opposite walls of said pumping chamber, a freely rollable element located in said chamber between said surfaces in driving contact with said surfaces, and a spring telescoped over said piston with opposite ends bearing against said piston and housing to resist relative rotation therebetween.

28. A pump, comprising a housing having a circular bore, a driver member mounted in said bore for rotation about the bore axis and having a driver surface thereon, a pumping piston having mounted for reciprocation in said bore and having a reciprocably driven surface facing said driving surface, a freely rollable element in driving contact with said surfaces, and resilient means for keep ing said surfaces and element in driving contact, said pump having fluid inlets and outlets to the pumping chamber formed by said surfaces and said bore.

29. A pump, as set forth in claim 1, wherein said driven surface is generally iiat so as to have minimum frictional contact with said element and capable of providing a true rolling contact.

References Cited in the file of this patent UNITED STATES PATENTS 608,361 Craig Aug. 2, 1898 984,320 Thompson Feb. 14, 1911 1,041,569 Bade Oct. 15, 1912 1,588,832 Young June 15, 1926 1,759,842 Fossa May 27, 1930 2,211,741 Elwell Aug. 13, 1940 2,283,242 Van Der Walt May 19, 1942 2,474,720 Billeter June 28, 1949 2,515,539 Wichman July 18, 1950 2,630,723 Gridley Mar. 10, 1953 FOREIGN PATENTS 535,555 Great Britain Apr. 1l, 1941 623,715 France Mar. 22, 1927 

